Corrosion preventing agent



llnited States patefit 2,783,204 conRosIoN'PnEvsNTrNG AGENT John P". McDennott, Springfield, N. 3., asslgnor m Esso Research and Engineering Company, a corporation of Delaware- No Drawing. Application luiy 1, 1955,

Serial No. 519,683

11 Claims. (Ci. 25246.6)

The present invention relates to the improvement of hydrocarbon products derived from petroleum sources and more particularly to the preparationof improved mineral lubricating oil compositions by the incorporation therein of a new class of additives which impart improved properties to such hydrocarbon products.

This application is a continuation-in-part of patent application Serial No. 192,617, filed on October 27, 1950, and now abandoned.

In the development of petroleum lubricating oils the trend has been to use more and more efiicient refining methods in order to reduce the tendency of the oils to form carbon and deposits of solid matter or sludge. While such highly refined oils possess many advantages, their resistance to oxidation, particularly under conditions of severe service, is generally decreased and they aremore prone to form soluble acidic oxidation products which are corrosive. They are generally less effective than the untreated oils in protecting the metal surfaces which they contact against rusting and corrosion due to oxygen and moisture. Although generally superior to lightly refined oils they may deposit films of .varnish on hot metal surfaces, such as the pistons of internal combustion engines, under very severe engine operating conditions.

In accordance with the present invention a new class of products has been discovered which when added to refined lubricating oils in small proportions substantially reduce thetendency of such oils to corrode metal surfaces, and which are particularly elfective in inhibiting the corrosion of copper-lead and cadmium-silver bearings. They are likewise effective in inhibiting oxidation of such oils and other petroleum hydrocarbon products, as will be more fully explained hereinafter.

The new class of materials which we have found to possess the antioxidant and stabilizing qualities described above are the condensation products of epoxides with reaction products ofphosphoruspentasulfide and hydroxy organic compounds, and more particularly are the condensation products or oil-soluble di-hydrocarbon dithiophosphoric acids with alkylene (or olefinic) oxides having. 2 to 6 carbon atoms. It is believed that the condensa'tion products formed in accordance with this invention are predominantly compounds of the formula R0 S R1 Rs i s-h-hon RO 1 12 1 14 Diisopi'opyldithiophosphoric acid 2 Di-n-butyl dithiophosphoric acid Diisobutyl dithiophosphoric acid Di-n-octyl dithiophosphoric acid Di-tert.-octyl dithiophosphoric acid Di-(ethylhex-yl) dithiophosphoric acid Dinonyl dithiophosphoric acid Di(Cs oxo) dithiophosphoric acid 'Dioleyl dithiophosphoric acid Dilauryl dithiophosphoric acid Di-(methylcyclohexyl) dithiophosphoric acid Di-(isopropylcyclohexyl) dithiophosphoric acid Di-(tert.-octylphenyl) dithiophosphoric acid Di-(2,4,6-triisobutylphenyl) dithiophosphoric acid The above listed di-hydrocarbon I dithiophosphoric acids may be prepared by reacting a hydroxy organic compound, i. e., an alcohol or phenol, with phosphorus pentasulfide by means well known in the art, and it is to. be understood that the invention applies not only to simple acids but to mixtures. of acids formedv by reacting phosphorus pentasulfide with mixtures of alcohols or phenols, such, for example as the mixtures. of C10 to Cm aliphatic alcohols. known as Lorol alcohols, and the mixture of alcohols derived. by the oxidation of paraffin wax. Included also are products derived from. the mixture of'branched chain aliphatic alcohols obtained in the oxol process.

.The hydroxy organic compounds useful in this. inven tion have the formula ROH where R is an aliphatic (saturated or unsaturated), cycloaliphatic or aliphatic-aromatic hydrocarbon radical. Aliphatic hydrocarbon alcohols are preferred due to their relatively low cost and commercial availability. Particularly preferred alcohols are those wherein R is an alkyl group containing about 2 to 24 carbon atoms, especially about 3 to 18 carbon atoms, preferably about 6 to 12 carbon atoms per molecule. Alkyl phenols having the formula where R is an alkyl group containing about 4 to 24 carbon atoms, especially about 6 to 12 carbon atoms, and alkyl cyclohexanols containingabout l to 4 carbon atoms in the alkyl' group are also useful in the present invention, forming particularly potent inhibitor additives for petroleum hydrocarbon products.

The reaction between the hydroxy organic compounds and phosphorus pentasulfide is carried out utilizing about 4 moles of the hydroxy organic compounds per mole of phosphorus pentasulfide. This reaction is generally carried out at a temperature of about 50 to 180 C., usually about to 175 C., preferably about to C. by stirring the reactants together until. essentially all of the P285 has been consumed. This can be noted visually. The reaction temperature required will depend upon the reactivity of the. hydroxy organic compound with P285. For'example, ethyl alcohol may be reacted at about 50 to 90 C. when usinga solvent. The reaction time required will generally be in the range of about 0.5 to 5 hours, usually about 1 to 2 hours. -After the reaction is completed the reaction product is preferably blown with nitrogen or other inert gas to remove hydrogen sulfide. therefrom. Preferably the reaction product is filtered to remove therefrom traces of, unreacted P285, If desired, the reaction may be carried out in a solvent such as benzene or a mineral oil, e. g.,'

arsaaoe I f 3 a mineral lubricating oil. The final productis believed to be predominantly di-hydrocarbon dithiophosphoric acid having the formula The alkylene (or olefinic) oxides which may be reacted with the dithiophosphoric acids in accordance with this invention include especially the well-known alkylene oxides, such as ethylene oxide, propylene oxide, the butylone and isobutylene oxides, and a butadiene monoxide. Alkylene oxides containing 2 to 6 carbon atoms, preferably about 2 to 4 carbon atoms, per molecule, may be used in the present invention. Propylene oxide and ethylene oxide are the preferred alkylene oxides because of their low cost and commercial availability. Propylene oxide is particularly preferred.

The reaction between the dithiophosphoric acid (the reaction product of the hydroxy organic compound and P285) and the alkylene oxide is a spontaneous exothermic reaction which takes place immediately upon contact of the reactants at normal room temperatures, and may be conveniently conducted by adding about one mole of the alkylene oxide slowly to about one mole of the dithiophosphoric acid while rapidly stirring the reaction mixture and controlling the temperature by means of a water or ice bath. Generally temperatures in the range of about 20 to 100 may be employed. No catalyst is required, and the time required for the completion of the reaction is not greater than two hours and is usually much less. Reaction times of about 0.2 to 2 hours may generally be employed. Solvents are not normally required, but in some cases it may be convenient to conduct the reaction in the presence of well-known inert solvents such as ethylene dichloride, benzene, xylene, or a mineral oil.

The amount of the additives of the present invention which is to be employed in mineral lubricating oil compositions or other petroleum hydrocarbon compositions (which generally will contain a major proportion of the hydrocarbon oil) will normally range from about 0.02% to 5%, more generally from about 0.1 to about 2%, by weight based on the total composition, and the particular amount in individual cases will be selected in accordance with the requirements of the case and in view of the properties of the base stock employed. For commercial purposes, it is convenient to prepare concentrated oil solutions in which the amount of additive in the composition ranges from 25 to 50% by weight, and to transport and store them in such form. In preparing a lubrieating oil composition for use as a crankcase lubricant the additive concentrate is merely blended with the base oil in the required amount.

The preparation and testing of the additives of the present invention are illustrated in the examples described below, but it is to be understood that the additives prepared and their application in various tests are illustrative only and are not to be construed as limiting the scope of the invention in any manner.

Example 1.--Di (Ca oxo) dithiophosphoric acidpropylene oxide reaction product A Cs oxo alcohol was prepared by reacting CO and Hz with a C7 olefin fraction obtained by polymerizing a mixed propylene-butylene feed stock, and hydrogenating the resulting aldehyde. The di-(Ca oxo) dithiophosphoric acid was prepared by heating a mixture of 260 g. (2 mols) of the Cu oxo alcohol, 111 g. (0.5 mol) of P255, and 354 g. of a light mineral oil in a S-neckcd 2-1. flask equipped with a stirrer, thermometer, and reflux condenser, for 1 hour at 110 C. After filtration, the product (an approximately 50% oil solution of di-(Ca hours.

oxo dithiophosphoric acid) was blown with nitrogen to 30 minutes on the steam bath to remove HzS.

The oil-acid solution was placed in a 4-necked 2-1. flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, after which 58 g. (1 mol) of propylene oxide was added over a period of about 40 minutes, during which time the temperature rose from 28 C. to 68 C. The product was heated for an additional 45 minutes at C., after which it was blown with nitrogen for 1 hour on the steam bath. A pale yellow concentrate was obtained, which upon analysis was found to contain 4.1 phosphorus and 7.7% sulfur.

Example 2.-Di-(methylcyclohexyl) dithiophosphoric acid-propylene oxide reaction product A mixture of 912 g. (8 mols) of methylcyclohexanol and 444 g. (2 mols) of P285 was heated for 1 hour at C. in a 3-necked 1-l. flask equipped with a thermometer, stirrer, and reflux condenser. The product (di- (methylcyclohexyl) dithiophosphoric acid) was then blown with nitrogen on the steam bath to remove H28.

The acid was decanted into a 4-necked 3-1. flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, after which 232 g. (4 mols) of propylene oxide was added over a period of 1% hours, keeping the temperature below 45 C. by means of an ice bath. Following a 45-minute soaking period at 95 C., the product was filtered, giving a clear, brown liquid which contained 8.3% phosphorus and 14.1% sulfur.

Example 3.Di-(tert.-octylphenyl) dithiophosphoric acid-butadiene monoxide reaction product A mixture of 824 g. (4 mols) of tert.-octylpheno1 and 222 g. (1 mol) of P285 was heated at 150 C. for 1% hours in equipment similar to that employed in previous examples, followed by filtration and blowing with nitrogen. The product was di-(tert.-octylphenyl) dithiophosphoric acid.

784 g. (1.54 mols) of the acid was charged into a 4-necked, 2-l. flask equipped with a stirrer, thermometer, reflux condenser and dropping funnel. At a temperature of 70 C. 108 g. (1.54 mols) of butadiene monoxide was added over a period of two hours with rapid stirring, the temperature being maintained at 70-80 C. by means of a water bath. The product was then stirred for an additional hour at 70 C. A viscous, light brown liquid was obtained which contained 4.7% phosphorus and 9.9% sulfur.

Example 4.Dioleyl dithiophosphoric acid-ethylene oxide reaction product A mixture of 536 g. (2 mols) of oleyl alcohol and 111 g. (0.5 mol) of P285 was heated at C. for 1% Following filtration to remove a small amount of unreacted PzSs, the product (dioleyl dithiophosphoric acid) was blown with nitrogen on the steam bath for 30 minutes.

The filtrate was then transferred to a 4-necked 2-1. flask equipped with a stirrer, thermometer, Dry Ice reflux condenser, and gas inlet tube. Ethylene oxide was then passed into the stirred thiophosphoric acid for 2 hours, maintaining the temperature under 30 C. both by cooling bath and slow introduction of ethylene oxide. The product was then blown with nitrogen on the steam bath for 20 minutes. A light brown liquid was obtained which, upon analysis, was found to contain 5.2% phosphorus and 9.4% sulfur.

Example 5.S. 0. D. Corrosion Test Blends were prepared containing 0.25% by weight of each of the condensation products of Examples 1 to 4 in a paraflinic mineral lubricating oil of SAE 20 grade. Where the product was obtained in the form of a mineral oil solution a quantity of the product was employed which was equivalent to 0.25% of the active compound.

These blends and a sample of the unblended base oil were submitted to a corrosion test, known as the S. O. D. Corrosion Test, designed to measure the effectiveness of the product inhibitingthe corrosiveness of a typical mineral lubricating oil toward the surfaces of copper-lead bearings. The test was conducted as follows: 500 cc. of the oils was placed in a glass oxidation tube (13 inches long and 2% inches in diameter) fitted at the bottom with a A inch air inlet tube perforated to facilitate 'air distribution. The oxidation tube was then immersed in a heating bath so that the oil temperature was maintained at 325 F, during the test. Two quarter sections of auto; motive bearings of copper-lead alloyof known weight having a total area of 25 sq. cm. were attached to 013- posite sides of a stainless steel rod which was then immersed in the test oil and rotated at 600 R. P. M., thus providing sufficient agitation of the sample during the test. Air was then blown through the oil at the rate of 2 cu. ft. per hour. At the end of each 4-hour period the bearings were removed, washed with naphtha and weighed to determine the amount of loss by corrosion. The bearings were then repolished (to increase the severity of the test), reweighed, and then subjected to the test for additional 4-hour periods in like manner. The results are given in the following table as fcorrosion life, which indicates the number of hours required for the hearings to lose 100 mg. in weight, determined by interpolation of the data obtained in the various periods.

Oil or oil blend Bearing corrosion life (his) Base oil 9 Base 0il+0.25% product of Example 1 18 Base oil-+0.25% product of Example 2 23 Base oil+0.25% product of Example 3-.

Base oil-+0.25% product of Example 4..

Example 6.-Laus0n engine test Lubricant Bearingweight loss (mg/bearing) Base oil Base oil+1% product of Example 2 9 Example 7.-Etlyl alcohol-PzSs-etylene oxide reaction product 400 cc. of benzene and 222 g. (1 mol) of P255 were charged to a 2-liter flask. While rapidly stirring the contents of the flask, 184 g. (4 mols) of absolute ethyl alcohol were added over a period of about 1 /2 hours. During this time, the reaction temperature was maintained at about 50 C. by means of a water bath. Then the reaction mixture was refluxed at about 82 C. for about one hour, after which the reaction mixture was filtered to remove a small amount of unreacted Pass. The reaction mixture was then blown with nitrogen overnight to remove the solvent (benzene) and hydrogen sulfide. A dark colored liquid product was obtained which contained 10.5 weight percent phosphorus and 30.0 weight percent sulfur.

74.4 g. (0.4 mol) of the above-described liquid product were placed in a 250 ml. flask and 17.6 g. (0.4 mol) of ethylene oxide were bubbled into the contents of the flask with rapid shaking over a periodof abotit' 30minutes while maintaining the reaction temperature at about 25 T C. by means of an ice bath. The contents or the flask were stirred for an additional 30 minutes without the ice bath and then blown with nitrogen on a steam bath for about 20 minutes. 90.5 g. of a s'traw colored liquid were obtained which contained 10.0 weight percent phosphorus and 22.0 weight percent sulfur;

Then about 11 g. of the straw-colored liquid were placed in a 50 ml. beaker and heated slowly on a hot plate to thereby determine the thermal stability of the reaction product. At a temperature of about 230 F., fumes were evolved from the reaction product. At about 284 F., the reaction product bubbled and at a temperature of about 293 F. the product apparently polymerized to a black solid. This indicates that the present reaction product was very stable as to thermal degradation.

The products of the present invention may be employed not only in ordinary hydrocarbon lubricating oils. but also in the heavy duty type of lubricating oils which have been compounded with such detergent type additives as metal soaps, metal petroleum sulfonates, metal phenates, metal alcoholates, metal alkyl phenol sulfides, metal organo phosphates, phosphites, thiophosphates, and thiophosphites, metal xanthates and thioxanthates, metal thiocarbamates, and the like. Other types of additives, such as phenols and phenol sulfides, may also be present.

The lubricating oil base stock used in the compositions of this invention may be straight mineral lubricating oils or distillates derived from paraflinic, naphthenic, asphaltic or mixed base crudes, or, if desired, various blended oils may be employed as well as residuals, particularly those from which asphaltic constituents have been carefully removed. The oils may be refined by conventional methods using acid, alkali and/oi clay or other agents such as aluminum chloride, or they may be extracted oils produced by solvent extraction with solvents such as phenol, sulfur dioxide, etc. Hydrogenated oils or white oils may be employed as well as synthetic oils resembling petroleum oils, prepared, for example, by the polymerization of olefins or by the reaction of oxides of carbon with hydrogen or by the hydrogenation of coal or its products.

For the best results, the base stock chosen should normally be an oil which, with the new additive present, gives the optimum performance in the service contemplated. However, since one advantage of the additives is that their use also makes feasible the employment of less satisfactory mineral oils, no strict rule can be laid down for the choice of the base stock. The additives are normally sufliciently soluble in the base stock, but in some cases auxiliary solvent agents may be used. The lubricating oils will usually range from about 40 to 150 seconds (Saybolt) viscosity at 210 F. The viscosity index may range from 0 to or even higher.

Other agents than those which have been mentioned may be present in the oil composition, such as dyes, pour point depressants, heat thickened fatty oils, sulfurized fatty oils, sludge dispersers, antioxidants, thickeners, viscosity index improvers, oiliness agents, resins, rubber, olefin polymers, and the like.

Assisting agents which are particularly desirable as plasticizers and defoarners are the higher alcohols having preferably 8-20 carbon atoms, e. g., octyl alcohol, lauryl alcohol, stearyl alcohol, and the like.

In addition to being employed in lubricants, the addi tives of the present invention may also be used in other petroleum oil products such as motor fuels, heating oils, hydraulic fluids, torque converter fluids, cutting oils, flushing oils, turbine oils, transformer oils, industrial oils, process oils, and the like, and generally as antioxidants in mineral oil products. They may also be used in gear lubricants, greases and other products containing mineral oils as ingredients.

What is claimed is:

'1. A petroleum hydrocarbon product containing dissolved therein a corrosion inhibiting amount of a condensation product obtained by condensing an alkylene oxide containing 2 to 6 carbon atoms per molecule at a temperature of about 20 to 100 C. for about 0.2 to 2 hours with an oil-soluble reaction product obtained by reacting about 0.5 moles of phosphorus pentasulfide at a temperature of about 50 to 180 C. for about 0.5 to

' hours with about 2 moles of a hydroxy organic compound of the formula ROH where R is a hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, and aliphaticaromatic hydrocarbon radicals.

2. A petroleum hydrocarbon product containing dissolved therein a corrosion inhibiting amount of a condensation product obtained by condensing about one mole of an alkylene oxide containing 2 to 4 carbon atoms per molecule at a temperature of about 20 to 100 C. for about 0.2 to 2 hours with about one mole of an oilsoluble reaction product obtained by reacting about 0.5 mole of phosphorus pentasulfide at a temperature of about 50 to 180 C. for about 0.5 to 5 hours with about 2 moles of a hydroxy-organic compound of the formula ROH where R is a hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, and aliphaticaromatic hydrocarbon radicals.

, 3. Composition according to claim 2 wherein said petroleum hydrocarbon product is a lubricating oil fraction.

4. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and a corrosion inhibiting amount of a condensation product obtained by condensing about one mole of an alkylene oxide containing 2 to 4 carbon atoms at about 20 to 100 C. for about 0.2 to 2 hours with an oil-soluble reaction product obtained by reacting about 0.5 mole of phosphorus pentasulfide at a temperature of about 125 to 175 C. for about 0.5 to 5 hours with about 2 moles of a hydroxyorganic compound of the formula ROH where R is a hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, and aliphaticaromatic hydrocarbon radicals.

5. Composition according to claim 4 wherein said alkylene oxide is propylene oxide and said hydroxy organic compound is a branched-chain aliphatic Cs alcohol.

6. Composition according to claim 4 wherein said 'alkylene'oxide is propylene oxide and said hydroxy organic compound is methylcyclohexanol.

7. Composition according to claim 4 wherein said alkylene oxide is butadiene monoxide and said hydroxy organic compound is tert. octyl phenol.

8. Composition according to claim 4 wherein said alkylene oxide is ethylene oxide and said hydroxy organic compound is oleyl alcohol.

9. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and about 0.02 to 5% by weight, based on the total composition, of a condensation product obtained by condensing about one mole of propylene oxide at about 20 to 100 C. for about 0.2 to 2 hours with about one mole of a reaction product obtained by reacting about 0.5 mole of phosphorus pentasulfide at a temperature of about to 180 C. for about 0.5 to 5 hours with about 2 moles of an aliphatic alcohol of the formula ROH where R is an alkyl group containing 2 to 24 carbon atoms.

10. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and about 0.02 to 5% by weight, based on the total composition, of a condensation product obtained by condensing about one mole of ethylene oxide at about 20 to C. for about 0.2 to 2 hours with about one mole of a reaction product obtained by reacting about 0.5 mole of phosphorus pentasulfide at a temperature of about 50 to C. for about 0.5 to 5 hours with about 2 moles of an aliphatic alcohol of the formula ROH where R is an alkyl group containing 2 to 24 carbon atoms.

11. A composition consisting essentially of a mineral lubricating oil and about 25 to 50% by weight of a condensation product obtained by condensing about one mole of an alkylene oxide containing 2 to 4 carbon atoms per molecule at a temperature of about 20 to 100 C. for about 0.2 to 2 hours with about one mole of an oil-soluble reaction product obtained by reacting about 0.5 mole of phosphorus pentasulfide at a temperature of about 50 to 180 C. for about 0.5 to 5 hours with about 2 moles of a hydroxy-organic compound of the formula ROH where R is a hydrocarbon radical selected from the group consisting of aliphatic, cycloaliphatic, and aliphatic-aromatic hydrocarbon radicals.

No references cited. 

1. A PETROLEUM HYDROCARBON PRODUCT CONTAINING DISSOLVED THEREIN A CORROSION INHIBITING AMOUNT OF A CONDENSATION PRODUCT OBTAINED BY CONDENSING AN ALKYLENE OXIDE CONTAINING 2 TO 6 CARBON ATOMS PER MOLECULE AT A TEMPERATURE OF ABOUT 20* TO 100*C. FOR ABOUT 0.2 TO 2 HOURS WITH AN OIL-SOLUBLE REACTION PRODUCT OBTAINED BY REACTING ABOUT 0.5 MOLES OF PHOSPHOURS PENTASULFIDE AT A TEMPERATURE OF ABOUT 50* TO 80*C. FOR ABOUT 0.5 TO 5 HOURS WITH ABOUT 2 MOLES OF A HYDROXY ORGANIC COMPOUND OF THE FORMULA 